Why can't Dispatcher connect to the SMTP server?

Ping

Let's first try the obvious: can you ping the SMTP server? Since the Dispatcher process runs on the Services Server, run the ping from there.

Telnet 25

So basic network connectivity is fine. What about port 25? Try to telnet to port 25 of the SMTP server from the Services Server.

Telnet 80

Something is wrong with port 25. Try another port - in this case, port 80 works.

Why is the port being blocked?

One thing we've all seen at one point or another is TCP ports getting stuck. Try restarting the Dispatcher process. Does it restart successfully or produce an error? If an error occurs, a system reboot would be a wise next step.

But more common with SMTP server errors when network connectivity is fine is the virus scan. McAfee VirusScan is running on our Services Server with Access Protection. Most VirusScan's should have a log, and if we pull ours up we can see:

Bingo\! Let's disable the port blocking rule "Prevent mass mailing worms from sending mail" on the Services Server so the Dispatcher process can do it's thing.

Resolution

Virus port-blocking protection can actually hinder the functionality of EIM. We learned how to verify port status and diagnose a problem with McAfee VirusScan.

One good takeaway from this scenario is the importance of the Virus Scan settings in the 4.3 Deployments Guide. While you're in the Virus Scan properties, ensure that they are set correctly on all servers.